External Monitor not receiving signal/intermittently receiving signal from mac

Big Sur 11.5

The monitor is present in that applications are open on it, can move cursor across to the screen but the screen is blank

DELL U3415W

Things I've tried:

reset SMC
reset NVRAM/PRAM
Both USBC ports
different cable
Use detect displays button

This actually works some of the time in conjunction with unplugging the USBc and plugging it back in... but this is not a great solution.

Most notably this seems to occur when the computer goes to sleep

Posted on Aug 1, 2021 12:11 PM

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21 replies

contextCue Author

Level 1

11 points

Aug 17, 2021 11:19 AM in response to mike_bainbridge

Cool, I'll run the update and see where that gets me...

Aug 31, 2021 2:59 AM in response to MartinChuzzlewit

Thanks for clarifying, and I am glad that at least there is a workaround.

Aug 3, 2021 4:16 AM in response to mike_bainbridge

Yours seems to be a different issue. I suggest you start a new thread, and give all the relevant details.

Many people apparently use the Mini M1 with two displays, and I don't recall seeing this mentioned (though it may have escaped me).

I recommend you run Etrecheck and post its report here using the "additional text" button.

Aug 3, 2021 6:22 AM in response to mike_bainbridge

Maybe it is a firmware issue, maybe not.

In another thread, someone with issues with displays on a similar mac reported that changing to a different dock helped.

Only you have access to your mac and can do steps to troubleshoot. If it is a firmware or OS issue, then it is likely to fixed at some point; but if the matter is caused by some third party kernel extension then you will end up in frustration every time a new update comes along and doesn't fix the problem. It is up to you to keep waiting or to do more testing.

The fact that it happens in more than one mac is something that very understandably may convince one that it is a systemic problem; but more often than not similar macs owned by the same person or organization have similar problems - because the installation is also similar or identical. If you had used, say "cleanmymac" on all your macs (just as an example) and all showed problems, it would not mean there was a firmware bug.

Aug 3, 2021 8:32 AM in response to Luis Sequeira1

Understood - I've removed the Presonus kernel extension as it's not critical on this machine but on the reboot after this removal the secondary screen (HDMI in Apple Multi-adapter) had to be plugged and unplugged to be coaxed into life which doesn't bode well. I'll monitor the situation and compare with the machine with it still in. Both are Mac Mini M1 running 11.5.1

contextCue Author

Level 1

11 points

Aug 6, 2021 4:48 PM in response to Luis Sequeira1

A friend suggested this might be a driver issue, I did download a driver for the external screen but no difference.

I've noticed, prior to this event that there we quite a few issues with an external dock I had (first tried belkin dock and then and updated brydge dock)

This was a different machine, MBP, 2020.

The fix for the macbook pro was that I could only use the back left USBc dock for the external monitors

For the iMac setting sleep to never is an ok solution... it would certainly be nice if it just worked as intended though, I also have a system76 laptop and an archangel tower and both those machines have no issue.

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External Monitor not receiving signal/intermittently receiving signal from mac